A gasoline engine vehicle is available with a turbo system having a turbo charge which increases fuel efficiency and an engine output.
The turbo system increases the output by increasing an air content sucked into an engine using energy of exhaust gas which is discharged outside the vehicle, but the turbo system installed at an exhaust line side has difficulty in increasing a catalyst temperature at an early stage of starting the vehicle.
Automobile industries have conducted multidirectional researches to satisfy discharge regulations. As a method for this purpose, there is a method for installing a catalyst apparatus for purifying exhaust gas at a predetermined position of an exhaust manifold.
In this case, since a catalyst material inside the catalyst apparatus is generally activated at 350° C. or more to provide a normal purification function, after the vehicle starts, the catalyst apparatus does not purify discharged harmful materials until the catalyst apparatus reaches an activation temperature of 350° C. and discharges non-purified harmful materials in the air.
Therefore, after the vehicle starts, the vehicle uses a separate heater or controls fuel injection to heat the catalyst apparatus so that the catalyst apparatus may rapidly reach the activation temperature of 350° C.
As a method for increasing a catalyst temperature at an early stage of the vehicle start, there is a method for delaying ignition timing.
That is, when the ignition timing is delayed even though the same fuel amount is combusted, the method utilizes characteristics to reduce a combustion pressure and increase a temperature of exhaust gas.
However, even though the ignition timing is artificially lagged, in order for the vehicle to obtain a required output, a larger content of air needs to be delivered to a combustion chamber. To this end, an open value of a throttle connected to an engine combustion chamber needs to be large.
In this case, in the case of the gasoline engine in which the turbo charger is equipped, as the open value of the throttle is increased under an operation condition to activate the catalyst apparatus, the phenomenon that a pressure of an intake manifold (pressure of an intake line) is not reduced but is increased to a level of an atmospheric pressure occurs.
Therefore, after the vehicle starts, at the time of lagging the ignition timing under the operation condition to activate the catalyst apparatus, the catalyst temperature is increased but pressure of the intake line is not reduced. As a result, a brake using the catalyst apparatus has a problem of a braking force.
The related art uses a brake booster and a mechanical vacuum pump to keep a pressure of vacuum inside the brake booster in a vacuum state to increase the braking force of the brake.
When a vehicle runs normally, an intake pressure is lower than the atmospheric pressure, such that the related art may not able to maintain the braking force. However, in the case in which the ignition timing is delayed to increase the catalyst temperature at an early stage of the vehicle start, when the open value of the throttle is increased for the vehicle to obtain the required output, as described above, the pressure of the intake line is increased to the atmospheric pressure, and thus, the pressure of vacuum inside the brake booster is not kept in the vacuum state, such that the related art has a problem in keeping the braking force of the brake.
The contents described as the related art have been provided only for assisting in the understanding for the background of the present disclosure and should not be considered as corresponding to the related art known to those skilled in the art.